Electrical circuit arrangement



Nov. 9, 1954 G. T. KODAMA 2,694,185

ELECTRICAL CIRCUIT ARRANGEMENT Filed Jan. 19 1951 FNSI FlEa FISE F1531FIE- PIES mgcwxn United States Patent C) 2,694,185 ELECTRICAL CIRCUITARRANGEMENT George T. Kodama, Dunstable, Mass., assignor to SpragueElectric Company, North Adams, Mass., a corporation of MassachusettsApplication January 19, 1951, Serial No. 206,859 3 Claims. (Cl. 333-70)This invention assemblies and trical circuits.

In recent years the trend has been to combine as many electricalcomponents as possible into a single package. This package may then beemployed as a subassembly in a radio or control apparatus. Tominirelates to improved electrical circuit more particularly relates toprinted elecfrequencies, these stray capacities are sufficiently largeto render the general assembly unsuitable.

It is an object of the present invention to overcome the foregoing andrelated disadvantages. further ob- Additional objects will becomeapparent from the following description and claims.

resistance layers on the other hand.

In a more restricted sense the invention is concerned with an electricalcircuit assembly comprising a thin sheet of ceramic Patented Nov. 9,1954 constant below about 10 separating said terminating areas and saidresistors from said sheet.

Accordingto my invention herent high stray capacities.

My method consists of rst screening, otherwise -applying a thin layer ofa dielectric hmaterial,

Alternately, a resin layer, which may be loaded with ceramic particles,is applied under the resistor pattern. In such instances, the resistorterminating areas may be the capacitor elements or other either side o fReference will be made shows a finished accordance with the inventionsteps by which it is made.

` l shows a base ceramic strontium titanate. In other instances,particularly for high frequency, high Q applications, titanium dioxidedielectric sheets may be employed.

Fig. 2 shows a top view of the ceramic plate 10 with a layer 11 of lowdielectric constant vitreous enamel suspended in a temporary binderapplied to the resistor layer pattern and resistor terminal connectionpattern.

and 7.

`At this point, the p late is tired in a furnace or otherwise to removethe binder from the electrode silver and frrn 'the enamel dielectric.This firing operation usually takes place'atwa temperature from --about.450C. .,to.

otherwise applied between terminal 16 and electrodev12 v as-the nextstep. It is to be noted thatlayer 11 preferably extends beyondthe edgesof the terminal and the resistor by a measurable amount, for example, ord1 v narily at least 50 mils, to obtain -best charac.er1st1cs. Suitableresistor coating formulations are shown on pages 7, 8 and 9 ofthe abovecircular.

Figs.' 5A and 5B show the plate with terminal wires t f soldered to thevarious electrodes and terminal.v These may be appliedv byl placing vthewires against 'thesilver surface and then dipping the whole assembly ina solder bath. Terminal 20 is afxed to electrode 12; terminal 21;toelectrode 13; andterminal 24 to terminal 16.

Fig. 6 shows a schematic Wiring` diagram for the printed circuit whosepreparation is described above. While thisis simpler than most-circuits,vit -is intended to illustrate the inclusion of a resistor element aspart of the 'circuit without the stray capacity usually found betweenthe resistor and the other circuit elements.

As previously indicated, it is possible to use a `low dielectricconstant underlayer which need not be fired at high temperatures. Forexample, various resnous materials, such as polyesters, polyvinylcompounds, condensation resins, etc., are suitable yfor use because oftheirrelatively low dielectric constants. It is of course necessary thatthese resins, in their final state, should adhere to the ceramicsurface. The latter is normally microscopically rough and adhesion isreadily obtained with careful selection of resin material. Typicalmaterials` include resins obtained by copolymerizing polyethoxyleneresins with butylated urea formaldehyde resins; plain or modifiedlinseed oil-melamine-formaldehyde resins, alkyd resins,polytetrauoroethylene, etc. These may be loaded with ceramic materials,such fas talc, china clay and Zinc oxide to improve the 'screeningconsistency an final underlayert Whilethe low dielectric constantmaterial is normally applied by .screening through silk 'or steelscreens, it can also Vbe, applied to Vtlie relectrode materials and/orceramicbase by printing, spraying, painting or lother.

The enamelsfused may be selected from those v methods.

whichare ordinarlly applied for lvitreous vcoatings Vand i Adherencev tothev Where low-loss glazes for vm'etalware, ceramics, etc. underlyingceramic piece is important. printed circuits are desired, lead silicatetype enamels, suchfas potassium Ylead silicate, are preferred. Forexample, 'one 'good yenamel frit` consistsof about 65 parts by w'eightof lead oxide, 30 parts by y'weight oisilica, 4 parts by weight ofpotassium ox'ideand one part Iby weight ofr'alumina. Suitable temporarybinders' are :nu-

mer'ous; typicalv is `hydrogenated rosin, with a rosin ester plasticizerand pine o1l as a solvent;

-In orderto secure a slightly rough 'and unglaz'ed surface to whichthe-resistancematerial willadherefthe enamel frit :may have admi'xedtherewith frorn about 2% lo about 237% of a non-fusing inorganic llersuch asfta c. l

'When`resin-based low -dielectric constant layers Iare employed, as, forexample, when it is not 'desired to'ire the layer land/or the silverelectrodes at highl temperatures, a representative screening inkconsists ot from about 2() -to about 60 parts of a -50-50 mixture oflinseed-oil and melarnine-forn'ialdehyde resin, from about '-to"abo`ut60 parts of nely ground talc and from about vto about 8O parts ofv'asolvent for the resin. The underlayer laid down from'the above-ink maybe baked for one 'hour'at l75 C. andfor six hours at' 150 C. to completesolvent removal and; hardening of the resin.

While'the invention hasl been described with pzrticular reference to oneof the preferred embodiments,

namely, the `use of a low dielectricA constant layer tol reduce, thestray capacity between resistor elements and other elements'fofthetlprinted circuit assembly, the invention nds wide use' in otherways. Oneeimportant embodiment is described in connection with Figs. 7and-'8; Fig. 7 shows'f a crossse'ction'of a-simplefC dual icapacitorunit 'containingmaillow `capacity,-alowffloss cad to modify thecharacteristics of the terminal.

pacitor element and a high capacity, lower Q unit. The construction isessentially. similar. .to `.that shownin connection with Figs. l through5 with the elimination of the resistor element and the addition ofcapacitive overlap between the low dielectric constant layer and one ofthe base electrode layers. Element 30 is the high dielectric constantceramic plate upon which are provided thin electrode layers 31 and 32which are terminated as indicated at33 and 34. repectively. Lowdielectric constant layer 35, preferably the vitreous enamel type, but-optionally a resin binder type, overlaps a portion of electrode 32.Disposed on top of layer 35 is electrode 36, ordinarily a fired onsilver layer when insulation 35 Ais a vitreous enamel. Terminal 37 isprovided for electrode 36.

Fig. 8 shows a simplified schematiediagram of the circuit of the elementof Fig'. 7. Low capacity, high capacitor 41 is disposed betweenterminals 37 and 34, while vhigh capacity, low Q capacitoritnis'disposed between terminals 33 and 34. .This simplezexamr..

ple illustrates the use of the invention to produce a come bined high`and' low dielectric constant .article wherein portions of the assemblyare suited to high frequency,

low loss circuit introduction, .while the lother highfaf pacity-unitsare availablefor audio and lower frequency circuits.

It 1s to be zunderstood that the printed circuits prp.-

duced in accordance with the invention may .contain A feature of thepresent invention is that itfenablesx the construction of inexpensiveand compact selective: circuits that are of exceptionallyhigheiiiciency.,Thus-l a veryeffective low-pass vfilter circuitisprovided bythe construction of Fig. 5A Ywhich can have terminal 2,1-grounded or common to' .the inputand output .circuits., terminali@ asthe other ;input.lead, andvterminal 24;. as the other output lead.Byreasonof -thefspacin'g layer 11, the capacitance .across the resistor17 is quite low-n notwilistanding the use of .a Vvery compact` construetion and .a very high dielectric constant capacitor d1-` electric. Anyappreciable capacitance.betweenzinput'andY output-leads will be indirect competition with thehigh,

frequency by-passing capacitance 28 (see Fig. 6) sothat.`I the undesiredhigh frequency `signals arenot as effectively shunted. This undesiredcapacitance is zevenzfunf ther reduced by .spacing the leads (20,24.)gfromxthe'., opposite ends of resistor 17, as-much as'possible asshown'l in Fig. 5A.

The same type of construction canxalso .beused asfa;: low-pass filterwith the capacitance 28 connected;across the output terminal of theresistor'rather .thanits input'r This is .effected by merelyinterchanging .the I leadsZtt, 24 so that lead 24 is the Vinput and,lead 20,.ther output, the lead 21 remaining common to bothlinputzandoutput circuits. The Vabove-described reduction :of acapacitance betweenthe ,resistor lterminals fhas.;the :same

desirable effect in this'form ofithelinvention."

The resistorecapacitor ;combination..,of: the finvention i canalso'befconnected as a highpass lteriin .whichpit` also exhibits' theabove advantages. -Fo'r-thisitypetzof operation .the unit of Fig. 5A has.leadi24 connected-sinn common to both input and output circuits,with-'leadsifZO f and 21 as the input and outputterminals.; Wherethef;resistance is to be acrossr-the input, lead.20 is the input terminal,otherwise lead 21 is the linput terminal.

The advantages of Vthe ypresent -invention :canibe-additionallyobtainedin integrating or differentiating circuits. As is well known these typesof circuits'are thosevthat v. have integrating and differentiatingactionrespectivelyon i electrical signals, .and can be convenientlyprovidedlby resistance and capacitance series combinations. Thus. wheresignals are-impressed across a series-connected'resistance andcapacitance and the resistancetisdarge as compared with the capacitiveimpedance, the voltage. appearing across the .capacitance will be theintegral of the impressed signals. Conversely where the resistanceissmall as compared with the'` capacitive impedance,- the voltageappearing across the resistance is the.diiferential of the impressedsignals. In either case the capacitance across the resistance should beminimized vto'improvethe eiciency.

Aparticularlyf-useful applicationof `the^present--invention is in thevertical sync integrating circuit of a television receiver where thepicture-synchronizing pulse signals are supplied and the circuitdelivers the low frequency vertical pulses. A number of integratingresistance-capacitance circuits are usually connected in cascade to givesatisfactory performance. In accordance with the present invention theentire cascade combination can be placed on a single compact supportingsheet and operates very satisfactorily. No more than three integratingstages are needed in the cascade, and in some cases only two aresulicient. The entire integrating circuit assembly is accordingly quitecompact.

Fig. 9 shows a representative form of such integrating circuit. A plate40 of high dielectric constant material Such as the barium-strontiumtitanate described above has on one face a conductive coating 42 towhich is electrically connected as by soldering to a lead 73. On theopposite face of plate 40 are four different conductive coatings 50, 51,52 and 53 connected by resistive links 61, 62 and 63.

As in the simpler embodiment described above, the resistive links areall separated from the high dielectric constant plate 40, by a lowdielectric constant stratum 66. In'the form shown the stratum 66 is acontinuous connected to coatings 50 and 53 respectively.

In operation lead 73 is common to input and output circuits, lead 71 isthe other input lead and lead 72 the other output lead. It will be notedthat the incoming signals are impressed across the series connectedresistance 61 and capacitance 51-42. Another series chain, resistance 62and capacitance 52-42, is connected across capacitance 51-42 to act as asecond section of the cascade, and a third series chain 63 and 53-42across the second capacitance 52-42 supplies a third section, Tientegrated signals are taken from across capacitance To further minimizeundesired capacitance, capacitive coating 42 is kept from extendingunder or close to the resistances and the lead coating 50. Furthermorethe capacitance-reducing layer 66 extended under all adjacent parts ofthe capacitor electrode coatings 51, 52, 53 and the space betweenconductive coatings 50 and 51 may be somewhat larger than between theother coatings. Normally less capacitance is used in the first sectionof the integrating cascade so that a smaller electrode 51 is needed.

As many apparently diiferent embodiments of this invention may be madewithout departing from the spirit and scope hereof, it is to beunderstood that the invention s not limited to the specic embodimentshereof except as defined in the appended claims.

What is claimed is:

l. A vertical sync integrating assembly comprising a base plate ofhigh-dielectric-constant materiai, a single large conductive coatingdeposited on one face of said plate, a series of closely spacedconductive coatings on the other face of said plate and positionedopposite said large conductive coating to form separate capacitorstherewith,

a terminal conductive coating on said other ductive coating, a secondterminal lead attached to the remotely connected one of said series ofconductive coatings on said other face of said plate, and a thirdterminal lead connected to said large conductive coating.

2. A printed circuit assembly comprising a plate ofhigh-dielectric-constant material, a large conductive coating on oneface of said plate, a series of closely spaced site said largeconductive coating to provide separate capacitances with the largecoating, a low-dielectric-constant stratum positioned beneath the.entire adjacent edge porconnected respectively to said large conductivecoating, to one of said series of coatings, and to the resistancecoating.

.3. printed circuit assembly comprising a plate of high-dielectricconstant material, a large conductive coatsite said large conductivecoating to provide separate capacitances with the large coating, alow-dielectric-constant stratum positioned beneath the entire adjacentedge portions of said series of conductive coatings on said other faceof said plate, and leads connected respectively to said conductivecoatings.

References Cited in the lile of this patent Number Number UNITED STATESPATENTS Name Date Sargrove July 5, 1949 Khouri Jan. 3, Khouri Sept. 4,1951 FOREIGN PATENTS Country Date Great Britain Jan. 23, 1945

